#include <stdio.h>

int query(int (*callback)(char *, size_t *))
{
  char buffer[1024];
  size_t size = sizeof buffer;

  if (callback(buffer, &size) == 0) {
    puts("query: callback failed");
  } else {
    char *ptr = buffer;

    while (size-- > 0)
      putchar (*ptr++);
    putchar('\n');
  }
}